Recently, in automobile industry, weight reduction for improvement of fuel consumption and resource saving are being strictly required from the viewpoint of global environmental friendliness. Therefore, also in an on-vehicle loudspeaker mounted on a car, market demand for weight reduction and resource saving cannot be avoided. From the above-mentioned background, in loudspeakers mainly used for vehicles, for the purpose of weight reduction and resource saving, a resin frame is becoming mainstream instead of a metal frame that has been frequently used conventionally.
Hereinafter, a conventional loudspeaker frame is described with reference to a drawing. FIG. 10 is a perspective view of a conventional loudspeaker frame. Frame 21 is formed of resin by injection-molding.
Frame 21 includes center part 21A, outer peripheral part 21B, and connection parts 21C connecting center part 21A to outer peripheral part 21B. In frame 21, in order to obtain strengths equal to those of metal frames that have been frequently used conventionally, each part has a material thickness necessary for securing a strength.
Examples of information on prior art documents related to the invention of this application include patent literatures 1 and 2.